Visuospatial neglect after stroke: Heterogeneity, diagnosis and treatment

Abstract

The general objective of this thesis was to better understand and treat visuospatial neglect, a frequent and disabling disorder in lateralized attention. The first aim was to further unravel visuospatial neglect by focusing on several subtypes. In neglect research, mostly patients with left-sided neglect are included. Knowledge regarding neglect is, therefore, mainly based on a subset of patients. This is unfortunate, however, as our study showed that left- and right-sided neglect are both common after stroke. Furthermore, both patients with left- and right-sided neglect are less independent in mobility and self-care. It is, therefore, of great importance to adequately diagnose and treat both subtypes. Another subtype regards region-specific neglect. We studied neural substrates of peripersonal (i.e. within arm length) and extrapersonal (i.e. beyond arm length) neglect, and found that several right temporal and thalamic regions were related to both peripersonal and extrapersonal neglect, and several additional right temporal, parietal and occipital regions were only related to extrapersonal neglect. None of the brain regions were only related to peripersonal neglect. It seems that mostly shared anatomical regions are related to peripersonal and extrapersonal neglect. Today’s diagnosis of neglect lacks sensitivity, and discrepancies exist between performance on paper-and-pencil tasks and patient functioning in daily life. This is problematic for accurate diagnosis of neglect and for proper evaluation of rehabilitation interventions. We evaluated a dynamic multitask to assess neglect in a sensitive manner: the Mobility Assessment Course. An association existed between performance on the Mobility Assessment Course and performance on standard paper-and-pencil neglect tasks. Especially patients who were ‘recovered’, based on the paper-and-pencil tasks, showed neglect during the Mobility Assessment Course. This fits the hypothesis that this task may detect neglect in patients who do not show neglect during standard paper-and-pencil tasks. Next, we evaluated the potential of digitized neuropsychological testing. Next to the attentional bias, other cognitive processes that may relate to attention can be evaluated in more detail, such as search organization, involved in many daily processes and often disturbed after stroke. We studied search organization in stroke patients and found that, although disorganized search is related to neglect, this is only a weak relation, and it might be a separate cognitive construct. We conclude that analysing measures of search provides useful additional insights into the lower-order visuospatial processes of stroke patients. Finally, we evaluated the long-term effects of early treatment with prism adaptation compared to sham adaptation on neglect behaviour in daily life.Both patient groups (i.e., receiving sham adaptation and prism adaptation) improved on dynamic and static outcome measures of neglect. However, no differences were seen between groups. One of the main reasons for these neutral results could relate to the heterogeneity of the disorder, enhanced by the spontaneous neurobiological recovery in especially the subacute phase post-stroke onset or standard treatment effects (care as usual). They could have overshadowed the potential effects of prism adaptation. To conclude, prism adaptation is not effective for all patients with neglect, and, based on these results, should not be implemented in clinical practice.